1. Field of the Invention
Most cereal grains can be stored for long periods of time without substantial quality changes if the kernels remain intact. However, once the grain is subjected to grinding or cracking, flavor quality rapidly deteriorates due to lipid enzymes that cause hydrolytic and oxidative changes typified by the onset of bitterness and rancidity. Processing methods such as extrusion cooking or pressing on heated rolls used to inactivate lipid enzymes are known to cause drastic changes in the baking properties as well as in other functional properties of the milled product. Therefore, the solution to storage instability has focused on removal of germ and other lipid material by dry milling. This approach results in substantial losses in nutritional value and yield. With grains such as millet, which are very small and have a hard endosperm structure, separation is especially difficult.
2. Description of the Prior Art
Previous attempts to stabilize whole cereal grains against enzymatic and oxidative changes seemingly have centered on grains which are targeted for end use in an unmilled state wherein the functional properties are of no consequence. For example, Van Atta et al., U.S. Pat. No. 2,585,978, shows a method of stabilizing rice against rancidity which normally ensues after hulling as the result of hydrolysis of the triglyceride oils in the bran layer to fatty acids. Freshly harvested rice at its natural moisture content is blanched with moist air at 185.degree.-212.degree. F. (85.degree.-100.degree. C.) for about 1/2 to 15 minutes to inactivate lipase. The treated rice is thereafter dried to a moisture content of 10-15% and optionally milled only to remove the hull. In a somewhat similar process disclosed by Webster, U.S. Pat. No. 4,413,018, lipolytic reactions are suppressed in oats by treatment with wet heat at approximately 250.degree. F. (121.degree. C.) for 10-20 minutes. Under these conditions, oxidative rancidity as indicated by peroxide content is also minimized. The treated oats are thereafter stored and utilized as an unmilled grain product with no special functional requirements.